Apparatus and methods for acoustical monitoring and control of through-silicon-via reveal processing

ABSTRACT

A TSV (through silicon via) reveal process using CMP (chemical mechanical polishing) may be acoustically monitored and controlled to detect TSV breakage and automatically respond thereto. Acoustic emissions received by one or more acoustic sensors positioned proximate a substrate holder and/or a polishing pad of a CMP system may be analyzed to detect TSV breakage during a CMP process. In response to detecting TSV breakage, one or more remedial actions may automatically occur. In some embodiments, a polishing pad platen may have one or more acoustic sensors integrated therein that extend into a polishing pad mounted on the polishing pad platen. Methods of monitoring and controlling a TSV reveal process are also provided, as are other aspects.

FIELD

The invention relates generally to semiconductor device manufacturing and more particularly to backside chemical mechanical polishing of TSVs (through-silicon vias).

BACKGROUND

Chemical mechanical polishing (CMP), also known as chemical mechanical planarization, is a process typically used in the fabrication of integrated circuits (IC) on a semiconductor substrate. A CMP process may remove topographic features and materials from a partially-processed substrate to produce a flat surface for subsequent processing. A CMP process may use abrasives and/or a chemically-active polishing solution on one or more rotating polishing pads pressed against a surface of a substrate. The substrate may be held in a substrate holder that rotates the substrate. The substrate holder may also oscillate the substrate back and forth across the surface of the rotating polishing pad(s).

In the fabrication of ICs, 3D packaging may be used to increase circuit functionality and/or performance in a compact footprint. Three-dimensional packaging may involve the interconnection of IC chips stacked on top of one another using TSVs (through silicon vias) to electrically connect the stacked IC chips. TSVs are vertical electrical conductors that extend through the substrate. To access TSVs from a backside of a substrate (for subsequent electrical connection to another IC below), CMP may be used in a TSV reveal process. A TSV reveal process may include grinding and etching a backside surface of a substrate to expose TSV's as stubs that project from the backside surface. A dielectric film may then be deposited on the backside surface. CMP may be used to remove the protruding stubs and polish the backside surface to a desired dielectric film thickness to complete the TSV reveal process. However, TSV breakage (i.e., breakage of one or more stubs) may occur that can ruin a substrate. Therefore, improved TSV reveal processes are desired.

SUMMARY

According to one aspect, a platen for a chemical mechanical polishing (CMP) apparatus is provided. The platen comprises a disk-shaped base configured to receive a polishing pad on a surface thereof, the disk-shaped base having at least one through-hole, and an acoustic sensor received in the at least one through-hole and protruding from the surface of the disk-shaped base, the acoustic sensor configured to be electrically coupled to a controller.

According to another aspect, a chemical mechanical polishing (CMP) apparatus configured to perform a CMP process is provided. The CMP apparatus comprises a platen comprising a polishing pad, a substrate holder configured to hold a substrate to be polished, wherein the platen or the substrate holder is configured to put the substrate and the polishing pad in contact with each other, an acoustic sensor positioned proximate the polishing pad or the substrate during the CMP process, and an acoustic processor electrically coupled to the acoustic sensor and configured to analyze one or more signals received from the acoustic sensor to detect TSV (through silicon via) breakage.

According to a further aspect, a method of monitoring and controlling a TSV (through silicon via) reveal process is provided. The method comprises processing a substrate using a chemical mechanical polishing (CMP) process, sensing acoustic emissions of the CMP process, and analyzing the acoustic emissions to detect TSV breakage.

Still other aspects, features, and advantages of the invention may be readily apparent from the following detailed description wherein a number of example embodiments and implementations are described and illustrated, including the best mode contemplated for carrying out the invention. The invention may also include other and different embodiments, and its several details may be modified in various respects, all without departing from the scope of the invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. The drawings are not necessarily drawn to scale. The invention covers all modifications, equivalents, and alternatives falling within the scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

The drawings, described below, are for illustration purposes only. The drawings are not intended to limit the scope of the invention in any way.

FIGS. 1A-1C illustrate sequential cross-sectional views a semiconductor substrate undergoing a TSV (through silicon via) reveal process without TSV breakage according to the prior art.

FIG. 2 illustrates a TSV without breakage according to the prior art.

FIG. 3 illustrates a cross-sectional view of a semiconductor substrate with TSV breakage according to the prior art;

FIG. 4 illustrates a TSV with breakage according to the prior art.

FIG. 5 illustrates a schematic partial side view of a chemical mechanical polishing (CMP) system according to embodiments.

FIGS. 6A and 6B illustrate a top view and a side cross-sectional view (taken along line 6B-6B of FIG. 6A), respectively, of a platen and polishing pad of a CMP system according to embodiments.

FIG. 7 illustrates a flowchart of a method of monitoring and controlling a TSV reveal process according to embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to the example embodiments of this disclosure, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

In one aspect, a TSV (through silicon via) reveal process using CMP (chemical mechanical polishing) may be acoustically monitored and controlled to detect TSV breakage and to automatically respond thereto. In some IC fabrication processes, TSV breakage may occur more often during CMP where the TSV aspect ratio (i.e., exposed TSV stub height to TSV diameter) may be high (e.g., TSVs with small diameters). High aspect ratio TSVs may allow an IC to have a greater density of chip-to-chip interconnects. However, high aspect ratio TSVs may be less rigid and thus more susceptible to breakage during a CMP process that removes exposed TSV stubs from the backside surface of a substrate.

One or more acoustic sensors may be positioned in a CMP system to receive acoustic emissions during a CMP process. The one or more acoustic sensors may be coupled to, e.g., a substrate holder and/or a polishing pad platen. In some embodiments, a polishing pad platen may have one or more acoustic sensors integrated therein that extend into a polishing pad mounted on the polishing pad platen.

In some embodiments, the acoustic emissions received by the one or more acoustic sensors may be analyzed by a system controller and/or an acoustic processor to detect TSV breakage. The acoustic processor may be part of a CMP system controller or, alternatively, may be a separate, stand-alone component coupled to a CMP system controller. In response to detecting TSV breakage, the system controller and/or acoustic processor may automatically initiate one or more remedial actions. For example, in some embodiments, an operator may be notified of the TSV breakage. Additionally or alternatively, a CMP process may be automatically modified by, e.g., reducing a down force of a substrate or a polishing pad against the other by a predetermined amount, reducing a rotation speed of a polishing pad and/or a substrate by a predetermined amount, and/or combinations of both as may be preprogrammed in the system controller and/or acoustic processor. In some embodiments, a CMP process may be automatically stopped and/or control transferred to an endpoint routine of the system controller in response to detecting TSV breakage.

In other aspects, methods of monitoring and controlling a TSV reveal process are provided, as will be explained in greater detail below in connection with FIGS. 1A-7.

FIGS. 1A-1C illustrate a substrate 100 undergoing a TSV reveal process, which may be referred to as a BVR (backside via reveal) CMP process, in accordance with the prior art. FIG. 1A shows substrate 100 having a backside surface 102A that has been partially-processed by the TSV reveal process. Substrate 100 may have a silicon base layer 104, a metal (e.g., copper) layer 106, a plurality of TSVs 108 extending from metal layer 106 and projecting beyond silicon base layer 104, a barrier layer 110 covering TSVs 108 and metal layer 106, and a dielectric layer 112 covering backside surface 102A. In some fabrication processes, TSVs 108 may have a height H above silicon base layer 104 that may range from about 2 μm to about 4 μm, and may vary from TSV 108 to TSV 108. Substrate 100 having backside surface 102A may be received at a CMP system for further TSV reveal processing as shown in FIGS. 1B and 1C.

FIG. 1B shows substrate 100 having a further-processed backside surface 102B, wherein dielectric layer 112 and barrier layer 110 may have been removed from top surfaces 109 of TSVs 108 by a CMP process. The CMP process may continue to remove materials from and/or polish backside surface 102B of substrate 100 until backside surface 102C of FIG. 1C is produced, provided no TSV breakage occurs. As shown in FIG. 1C, TSVs 108 may be flush with surface 113 of dielectric layer 112 or, in some fabrication processes, slightly lower until a desired less-thick dielectric layer 112 is achieved. As shown, some copper dishing 111 may occur on the end surface of TSVs 108. A final soft buff may be provided to control surface finish and to remove small surface defects and imperfections. If no TSV breakage occurs, the final surface condition of substrate 100 may appear as shown in FIG. 1C upon completion of the TSV reveal process.

FIG. 2 shows a micrograph of substrate 200 having a TSV 208 and a surrounding backside substrate surface 202 upon completion of a TSV reveal process without TSV breakage.

FIG. 3 shows a substrate 300 having a processed backside surface 302 with TSV breakage in accordance with the prior art. TSV breakage may cause non-reworkable scratches and/or defects across a substrate surface that may adversely affect IC chip yield and reliability. Substrate 300 may have a silicon base layer 304, a metal (e.g., copper) layer 306, TSVs 308 a and 308 b, a barrier layer 310, and a dielectric layer 312. TSV 308 b may have broken off during a CMP process. This breakage may have caused oxide gouging 315, which may expose silicon layer 304 to metal contamination during processing. In some embodiments, TSV 308 b may be formed with, e.g., copper, which is a relatively soft material. Copper smearing on silicon layer 304 caused by TSV breakage may potentially impact IC quality and/or reliability during post-packaging electrical testing.

FIG. 4 shows a micrograph of a substrate 400 having a TSV 408 and a surrounding backside substrate surface 402 after TSV breakage. As shown, substantial surface scratching and defects may occur after breakage of TSV 408 during a CMP process. Furthermore, metal grains that may have been pulled out by the TSV breakage may cause, e.g., a metal pad 414 (i.e., the top surface of TSV 408) to not meet one or more specifications required for further processing, which may further impact IC yield and/or reliability.

FIG. 5 shows a chemical mechanical polishing (CMP) system 500 in accordance with one or more embodiments. CMP system 500 may be configured to hold a substrate 501 in contact with a polishing pad 516 and may be used to perform a CMP process on substrate 501 as part of a TSV reveal process. Substrate 501 may be a silicon-containing wafer, such as a patterned wafer including partially or fully formed transistors and a plurality of TSVs formed therein. Substrate 501 may be affixed (e.g., via adhesives) to a second carrier wafer or other suitable backing such that a TSV reveal process may be performed on substrate 501. Polishing pad 516 may be mounted on a platen 518, which may be disk-shaped and rotated by a suitable motor (not shown) coupled to platen 518 by a shaft 520. Platen 518 may be rotated at between about 10-200 rpm. Other rotational speeds may be used.

Substrate 501 may be held in a substrate holder 522. Substrate holders may also be referred to as retainers or carrier heads. In some embodiments, substrate 501 may be held to substrate holder 522 via a vacuum. Other suitable substrate holding techniques may be used. In some embodiments, substrate holder 522 may be configured to move substrate 501 (i.e., up and down as shown) into contact with, and away from, polishing pad 516. Substrate holder 522 may be rotated and, and in some embodiments, oscillated back and forth across the surface of polishing pad 516 as polishing pad 516 is being rotated in contact with the backside surface of substrate 501. In some embodiments, the oscillation rate of substrate holder 522 may be between about 0.1 mm/sec and 5 mm/sec. Other oscillation rates may be used. In some embodiments, substrate holder 522 may be rotated at between about 10-200 rpm. Other rotational speeds may be used. The oscillation may take place between a center and a radial side of polishing pad 516. In some embodiments, substrate holder 522 may be a Contour, 5-zone pressure head available from Applied Material of Santa Clara, Calif.

In other embodiments, the positions of polishing pad 516/platen 518 and substrate 501/substrate holder 522 may be reversed. That is, polishing pad 516 and platen 518 may be part of or mounted to an overhead assembly or polishing head configured to move polishing pad 516 upward away from, and downward into contact with, the backside surface of substrate 501 held in substrate holder 522.

Slurry 524 (a chemical polishing solution) may be applied to polishing pad 516 and inserted between polishing pad 516 and substrate 501 by a distributor 526. Distributor 526 may be coupled to a slurry supply 528 via one or more suitable conduits. A pump 530, a valve 532, or other liquid conveying and transfer mechanism may supply a metered amount of slurry 524 to the surface of polishing pad 516. In some embodiments, slurry 524 may be dispensed by distributor 526 onto the surface of polishing pad 516 ahead of substrate 501 such that slurry 524 may be received in front of substrate 501 and may be drawn between polishing pad 516 and substrate 501 by the rotation of polishing pad 516.

In some embodiments, one or more parts of CMP system 500 may be equivalent to or based on those of, e.g., a Reflexion® GT™ CMP System, by Applied Material, of Santa Clara, Calif.

CMP system 500 may also include one or more acoustic sensors 534 a and/or 534 b operable to sense acoustic emissions occurring during a CMP process performed on substrate 501. In some embodiments, CMP system 500 may include only one of acoustic sensors 534 a or 534 b. In other embodiments, CMP system 500 may include both acoustic sensors 534 a and 534 b. In still other embodiments, CMP system 500 may include more than two acoustic sensors, which may be positioned other than as shown for acoustic sensors 534 a and 534 b.

Acoustic sensors 534 a and/or 534 b may be positioned proximate polishing pad 516 and/or substrate 501 during the CMP process. In some embodiments, acoustic sensor 534 a may be physically coupled to platen 518 (or an overhead polishing head) in any suitable manner. For example, acoustic sensor 534 a may be mounted in a bracket that is mechanically fastened to platen 518. In some embodiments, platen 518 may be an assembly that includes an upper platen and a lower platen (not shown) attached together. The upper platen may have a polishing pad 516 mounted thereon, wherein acoustic sensor 534 a may be integrated or mounted below the upper platen or integrated or mounted to, e.g., an outside edge of the lower platen via, e.g., a bracket or other suitable mechanism. In some embodiments, the bracket or other suitable mechanism may include a spring-loading mechanism to ensure that acoustic sensor 534 a maintains constant contact with a polishing pad. In some embodiments, the bracket or other suitable mechanism may include a cushioning pad to reduce signal attenuation or degradation. A power supply and signal cable (which may be represented at least partially by signal connection 536 a) may, in some embodiments, be routed through platen 518 (or the lower platen of the platen assembly described above) and connected to sensor 534 a via a high frequency (e.g., about 1 MHz) 8-terminal slip ring. In some embodiments, acoustic sensor 534 b, in addition or alternative to acoustic sensor 534 a, may be physically coupled to substrate holder 522 in any suitable manner. For example, acoustic sensor 534 b may be mounted in a bracket that is mechanically fastened to substrate holder 522. Acoustic sensors 534 a and/or 534 b may alternatively be located at other suitable positions relative to substrate 501 and polishing pad 516. In some embodiments, acoustic sensors 534 a and/or 534 b may be built directly into, or integrated with, platen 516, substrate holder 522, and/or any other suitable component of CMP system 500 (see, e.g., platen 616 described below in connection with FIGS. 6A and 6B).

Acoustic sensors 534 a and/or 534 b may be configured to be electrically coupled via wireless or wired signal connections 536 a and/or 536 b, respectively, to an acoustic processor 538 and/or a system controller 540 configured to detect TSV breakage based on acoustic emissions from a CMP process.

Acoustic processor 538 may be part of system controller 540 as shown, or a separate, stand-alone component that may be electrically coupled to system controller 540. System controller 540 may include a processor 542, which may control the operation of CMP system 500, including one or more CMP processes used in a TSV reveal process. In some embodiments, system controller 540 may not be coupled to and/or may not include acoustic processor 538, but instead may have processor 542 additionally perform the functions of acoustic processor 538 described herein.

Acoustic processor 538 may be configured to receive one or more signals representing acoustic emissions transmitted by acoustic sensors 534 a and/or 534 b. Acoustic processor 538 may be configured to detect TSV breakage by analyzing the one or more signals received from acoustic sensors 534 a and/or 534 b. The one or more signals received from acoustic sensors 534 a and/or 534 b may have amplitudes (representing, e.g., acoustic emission intensity) that may vary over time. Acoustic processor 538 may be configured to receive the time-varying signals and may compare the amplitudes thereof against one or more thresholds and/or threshold bands. Signal amplitudes exceeding those thresholds or outside of those threshold bands may indicate TSV breakage. In some embodiments, processing of received signals may involve comparing certain aspects or areas of received signal waveforms to preset thresholds. Acoustic processor 538 may include suitable signal filtering, amplifying, conversion (e.g., A/D conversion), and processing components and may include suitable memory configured to store data and one or more analyses. The data and analyses may be stored, for example, in any suitable storage medium (e.g., RAM, ROM, or other memory) of acoustic processor 538 and/or system controller 540. The one or more stored analyses and data may be used to monitor and control one or more CMP processes relative to detection of TSV breakage.

In some embodiments, a frequency-based analysis may be used to process acoustical data. A high sampling rate acquisition of acoustical signals from acoustic sensors 534 a and/or 534 b may allow use of stationary signal analysis such as fast Fourier transformations (FFT) or non-stationary signal analysis such as wavelet packet transformations (WPT). WPT may decompose a received acoustic signal into two parts, a low-frequency component that may yield approximations of signal identity, and a high frequency component that may yield details of the signal. The decomposition may be iterated with subsequent approximations being decomposed in turn.

In other embodiments, a time-based analysis may be used to process acoustical data. For example, a simple root mean square (rms) of received acoustical signals from acoustic sensors 534 a and/or 534 b may be monitored, provided TSV breakage events possess sufficiently large signal spikes in terms of signal-to-noise ratio.

To correlate received acoustical signals with TSV breakage events, the following setup procedure may be used in some embodiments. A first setup substrate with no protruding TSV stubs may undergo a CMP process to create baseline acoustical signal data for normalization. A second setup substrate with very high protruding TSV stubs (e.g., 15 μm stub lengths with 5 μm diameters) may undergo a CMP process. The second setup substrate may be inspected after processing for TSV breakage using, e.g., an optical inspection or a scanning electron microscope. A comparison may be made of the recorded signal magnitudes from the first and second setup substrates. Any signal spikes visible in the acoustic activity above the baseline signal during steady state CMP processing may be categorized as breakage signals, which may then be used to correlate TSV breakage events.

Acoustic processor 538 may automatically respond to detection of TSV breakage by initiating one or more remedial actions. The remedial actions may include notifying an operator by, e.g., causing an audible alert or displaying a warning or other type of message on a display device coupled to system controller 540. The remedial actions may additionally or alternatively include automatically stopping a CMP process in response to detecting TSV breakage. The remedial actions may additionally or alternatively include automatically modifying one or parameters of a CMP process in response to detecting TSV breakage. For example, acoustic processor 538 may be configured to automatically reduce a down force applied by substrate holder 522 against polishing pad 516 (or vice versa) and/or automatically reduce a rotation speed of substrate holder 522, platen 518, or both in accordance with one or more programmed routines executed by acoustic processor 538 or system controller 540 in response to detecting TSV breakage. This may allow CMP system 500 to automatically continue processing subsequent substrates with the modified processing parameters.

FIGS. 6A and 6B show an assembly 600 of a polishing pad 616 and a platen 618 that can be used in CMP apparatus, such as, e.g., CMP system 500, in accordance with one or more embodiments. Platen 618 may include a disk-shaped base 644 configured to receive polishing pad 616 on a surface 617 of disk-shaped base 644. Disk-shaped base 644 may have one or more through-holes 633 a, 633 b, and 633 c. That is, in some embodiments, disk-shaped base 644 may have only one of through-holes 633 a, 633 b, and 633 c, or only two of through-holes 633 a, 633 b, and 633 c, or more than the three through-holes 633 a, 633 b, and 633 c.

Platen 618 may also include one or more acoustic sensors 634 a, 634 b, and/or 634 c received in respective through-holes 633 a, 633 b, and 633 c. In some embodiments, acoustic sensors 634 a, 634 b, and/or 634 c may be friction fit in respective through-holes 633 a, 633 b, and 633 c. In other embodiments, acoustic sensors 634 a, 634 b, and/or 634 c may be physically coupled to or integrally formed with disk-shaped base 644 in any suitable manner. In some embodiments, platen 618 may have through-holes 633 a, 633 b, and 633 c that do not have an acoustic sensor received therein.

In some embodiments, acoustic sensors 634 a, 634 b, and/or 634 c may protrude from surface 617 of disk-shaped base 644 by a distance D1. Distance D1 may be selected to reduce acoustical signal attenuation that may occur in, e.g., a polyurethane soft SUBA™ portion of some embodiments of polishing pad 616. In some embodiments, distance D1 may be about 50 mils (about 1.27 mm). This may ensure that one or more of acoustic sensors 634 a, 634 b, and/or 634 c may be in close proximity to polishing surface 621 of polishing pad 616, yet not likely to be damaged during polishing.

In some embodiments, acoustic sensor 634 a may be located at about the center of platen 618. This center position may ensure that the distance of acoustic sensor 634 a to a substrate being processed remains constant. Acoustic sensor 634 b may be located radially outward from the center of platen 618 by about a distance D2, and acoustic sensor 634 c may be located radially outward from the center of platen 618 by about a distance D3. In one or more embodiments, distance D2 may be about 5 inches (about 12.7 cm) radially outward from the center of platen 618, and distance D3 may be about 10 inches (about 25.4 cm) radially outward from the center of platen 618. In some embodiments, the D3 distance of about 10 inches (about 25.4 cm) may ensure that acoustic sensor 634 c is positioned nearest the substrate on every rotating pass. In some embodiments, when the substrate moves away from acoustic sensor 634 c during CMP processing, received acoustic data may be filtered out. Distances D2 and/or D3 may alternatively have other suitable dimensions.

Acoustic sensors 634 a, 634 b, and/or 634 c may each be configured to be electrically coupled to a controller or acoustic processor via a wired or wireless connection. In some embodiments, acoustic sensors 634 a, 634 b, and/or 634 c may include electrical connectors 646 a, 646 b, and/or 646 c, respectively, accessible below platen 618 (i.e., opposite surface 617).

Referring to FIG. 6B, polishing pad 616 may be mounted to disk-shaped base 644 and may have one or more non-through holes 635 a, 635 b, and 635 c on a base-side surface 619 of polishing pad 616. Non-through holes 635 a, 635 b, and 635 c may have a depth of about distance D1 and may be configured to receive therein the protruding portion of one or more of respective acoustic sensors 634 a, 634 b, and/or 634 c. The number and positions of non-through holes 635 a, 635 b, and 635 c may correspond respectively to the number and positions of through-holes 633 a, 633 b, and 633 c of platen 618. Polishing pad 616 may be identical or similar to, e.g., an IC1000™ polishing pad with SUBA™ IV subpad having one or more non-through holes 635 a, 635 b, and/or 635 c formed therein.

In some embodiments, any one or more of acoustic sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c may be a piezoelectric, a transducer, and/or an accelerometer type sensor, and each may have a high signal to noise ratio. Acoustic sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c may include, in some embodiments, a flat frequency response over a region of about 100-500 kHz. In some embodiments, any one or more of acoustic sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c may amplify an acoustic signal with a gain of about 40-60 dB. Acoustic sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c may include, in some embodiments, a high pass filter having a range of about 50 Hz-100 Hz. Any suitable acoustic sensor may be used for sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c.

FIG. 7 illustrates a method 700 of monitoring and controlling a TSV reveal process in accordance with one or more embodiments. At process block 702, method 700 may include processing a substrate using a CMP process. The CMP process may be part of a TSV reveal process. For example, referring to FIGS. 1A-1C and 5, substrate 100 having backside surface 102A may be received at CMP system 500. Substrate 100 may be mounted or attached to substrate holder 522 and pressed against polishing pad 516 for CMP processing as shown and described in connection backside surfaces 102B and 102C or possibly 302.

At process block 704, sensing acoustic emissions of the CMP process may occur. Referring to FIGS. 5, 6A and 6B, sensing acoustic emissions may performed by any one or more of acoustic sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c. The acoustic emissions may be from a CMP process in which a substrate, such a, e.g., substrate 100 having backside surface 102A of FIG. 1A or substrate 501 of FIG. 5, is being processed with a polishing pad, such as polishing pad 516 of FIG. 5 or polishing pad 616 of FIGS. 6A and 6B. Acoustic sensors 534 a, 534 b, 634 a, 634 b, and/or 634 c may sense the acoustic emissions resulting from the processing of substrate 100 or 501 and may transmit electrical signals representing those acoustic emissions to a controller and/or acoustic processor, such as, e.g., system controller 540 and/or acoustic processor 538.

At process block 706, method 700 may include analyzing the acoustic emissions to detect TSV breakage. Analysis of the acoustic emissions may include comparing one or more parameters (e.g., amplitude) of one or more received signals to one or more thresholds and/or threshold ranges. The one or more received signals may represent acoustic emissions from a CMP process, and the one or more thresholds and/or threshold ranges may indicate whether or not TSV breakage has occurred during the CMP process. The one or more thresholds and/or threshold ranges may have been predetermined during one or more baseline CMP processes performed on first and second setup substrates where TSV breakage has and has not occurred, respectively.

If TSV breakage is detected at decision block 708, method 700 may proceed to process block 710. For example, in some embodiments, a high spike in a received acoustical signal may trigger method 700 to proceed to process block 710 in accordance with a pre-defined algorithm that may be part of a program executing on, e.g., acoustic processor 538, or part of endpoint software executing on, e.g., system controller 540. If TSV breakage is not detected, method 700 may proceed to decision block 712.

At process block 710, method 700 may include automatically responding to the detection of TSV breakage. In some embodiments, this may include automatically notifying an operator, who may be able to rework the currently processed substrate. In some embodiments, method 700 may respond to detection of TSV breakage by additionally or alternatively automatically modifying the CMP process by, e.g., reducing a down force, reducing a rotation speed, or both. Method 700 may additionally or alternatively respond to detection of TSV breakage by automatically stopping the CMP process. This may occur by proceeding directly to terminal block 714 (path shown in dashed line) or, in some embodiments, by proceeding to decision block 712 wherein a YES response may automatically be triggered, thus effectively stopping the CMP process. Method 700 may otherwise proceed to decision block 712.

At decision block 712, method 700 may include determining whether an endpoint of a CMP process has been detected. Endpoint detection may be performed by a system controller of a CMP system, such as, e.g., system controller 540 of CMP system 500. In some embodiments, endpoint detection for a TSV reveal process may include detecting the point at which TSVs are planarized flush to a dielectric oxide surface, such as shown in FIGS. 1C and 2. This endpoint detection may be determined by, e.g., acoustical analysis and/or motor torque feedback of a motor driving, e.g., the rotation of a polishing pad. Both acoustical analysis and motor torque feedback may be based on frictional changes that may occur as material(s) being processed change. For example, as a CMP process changes from removing/polishing primarily a metallic material on a substrate surface to removing/polishing primarily an oxide material on the substrate surface, a frictional change may occur between the substrate surface and a polishing pad that may be indicated in one or more received acoustical signals and/or in received motor torque feedback. Additionally or alternatively, endpoint detection for a TSV reveal process may be determined based on a white light spectrograph indicating a specific oxide thickness. If an endpoint has been detected at decision block 712, method 700 may proceed to termination block 714. Otherwise, method 700 may return to process block 704.

At termination block 714, method 700 and the processing of a substrate using a CMP process may end.

The above process and decision blocks of method 700 may be executed or performed in an order or sequence not limited to the order and sequence shown and described. For example, in some embodiments, process block 704 may be performed simultaneously with process blocks 706 and/or 710 and/or with decision blocks 708 and/or 712.

Persons skilled in the art should readily appreciate that the invention described herein is susceptible of broad utility and application. Many embodiments and adaptations of the invention other than those described herein, as well as many variations, modifications, and equivalent arrangements, will be apparent from, or reasonably suggested by, the invention and the foregoing description thereof, without departing from the substance or scope of the invention. Accordingly, while the invention has been described herein in detail in relation to specific embodiments, it should be understood that this disclosure is only illustrative and presents examples of the invention and is made merely for purposes of providing a full and enabling disclosure of the invention. This disclosure is not intended to limit the invention to the particular apparatus, devices, assemblies, systems, or methods disclosed, but, to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention. 

What is claimed is:
 1. A platen for a chemical mechanical polishing (CMP) apparatus, comprising: a disk-shaped base configured to receive a polishing pad on a surface thereof, the disk-shaped base having at least one through-hole; and an acoustic sensor received in the at least one through-hole and protruding from the surface of the disk-shaped base, the acoustic sensor configured to be electrically coupled to a controller.
 2. The platen of claim 1 further comprising a polishing pad mounted to the disk-shaped base, the polishing pad having a non-through hole on a base-side surface of the polishing pad configured to receive the acoustic sensor therein.
 3. The platen of claim 1 wherein the at least one through-hole is positioned at about the center, or about 5 inches (about 12.7 cm) radially outward from the center, or about 10 inches (about 25.4 cm) radially outward from the center of the disk-shaped base.
 4. The platen of claim 1 wherein the acoustic sensor protrudes from the surface of the disk-shaped base by about 50 mils (about 1.27 mm).
 5. Chemical mechanical polishing (CMP) apparatus configured to perform a CMP process, comprising: a platen comprising a polishing pad; a substrate holder configured to hold a substrate to be polished, wherein the platen or the substrate holder is configured to put the substrate and the polishing pad in contact with each other; an acoustic sensor positioned proximate the polishing pad or the substrate during the CMP process; and an acoustic processor electrically coupled to the acoustic sensor and configured to analyze one or more signals received from the acoustic sensor to detect TSV (through silicon via) breakage.
 6. The CMP apparatus of claim 5 wherein the acoustic processor is also configured to automatically stop the CMP process in response to detecting TSV breakage.
 7. The CMP apparatus of claim 5 wherein the acoustic processor is also configured to automatically notify an operator in response to detecting TSV breakage.
 8. The CMP apparatus of claim 5 wherein the acoustic processor is also configured to automatically modify the CMP process in response to detecting TSV breakage.
 9. The CMP apparatus of claim 8 wherein the acoustic processor is configured to automatically modify the CMP process by reducing a down force, reducing a rotation speed, or both in response to detecting TSV breakage.
 10. The CMP apparatus of claim 5 wherein the acoustic sensor comprises a flat frequency response over a region of about 100-500 kHz.
 11. The CMP apparatus of claim 5 wherein the acoustic sensor amplifies an acoustic signal with a gain of about 40-60 dB.
 12. The CMP apparatus of claim 5 wherein the acoustic sensor comprises a high pass filter having a range of about 50-100 Hz.
 13. The CMP apparatus of claim 5 wherein the acoustic sensor is integrated in the platen such that the acoustic sensor protrudes from a surface of the platen into the polishing pad.
 14. The CMP apparatus of claim 13 wherein the acoustic sensor protrudes from the surface of the platen by about 50 mils (about 1.27 mm).
 15. The CMP apparatus of claim 5 wherein the acoustic sensor is integrated in the platen at about the center, or about 5 inches (about 12.7 cm) radially outward from the center, or about 10 inches (about 25.4 cm) radially outward from the center of the platen.
 16. A method of monitoring and controlling a through silicon via (TSV) reveal process, comprising: processing a substrate using a chemical mechanical polishing (CMP) process; sensing acoustic emissions of the CMP process; and analyzing the acoustic emissions to detect TSV breakage.
 17. The method of claim 16 further comprising automatically stopping the CMP process in response to detecting TSV breakage.
 18. The method of claim 16 further comprising automatically notifying an operator in response to detecting TSV breakage.
 19. The method of claim 16 further comprising automatically modifying the CMP process in response to detecting TSV breakage.
 20. The method of claim 19 wherein the automatically modifying comprises automatically modifying the CMP process by reducing a down force, reducing a rotation speed, or both in response to detecting TSV breakage. 